Hydraulic blood pump



Nov. 23, 1965 A. w. BALDWIN HYDRAULIC BLOOD PUMP 2 Sheets-Sheet 1 Filed April 28, 1964 INVENTOR ALAN H. BALDWIN ATTORNEY NOV. 23, 1965 w, BALDWIN 3,218,979

HYDRAULIC BLOOD PUMP Filed April 28, 1964 2 Sheets-Sheet 2 ATTORNEY United States Patent 3,218,979 HYDRAULIC BLOOD PUMP Alan W. Baldwin, 4406 S. Panorama Drive, Oxon Hill, Md. Filed Apr. 28, 1964, Ser. No. 363,312 Claims. (Cl. 103-44) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This application is a continuation-in-part of application Serial No. 118,746, filed June 21, 1961, for Hydraulic Pump, now Patent No. 3,148,624, issued September 15, 1964. v

The present invention relates to a hydraulic pump for maintaining blood circulation in a patient. More particularly, the invention is concerned with a hydraulic system which incorporates a flexible pump chamber and a gentle valve action to assume the functions of the heart and maintain blood flow through the body of a patient.

It is a particular purpose of the present invention to provide a mechanical device which can undertake the functions of the heart and pump blood into the aorta of a patient while the heart is undergoing surgical repair. A pump of the above mentioned character must provide a gentle pumping action if it is to prevent injury to blood cells and minimize turbulence and foaming in the circulating medium.

The circulation of blood in previous heart-lung machines, with a few exceptions, has been carried out by some form of tube pumps because they were easy to sterilize. In such pumps pressure was applied externally to flexible tubing by rollers or mechanical fingers in a sequential manner to ensure a unidirectional flow without the use of valves. The output was determined by the degree of mechanical compression on the tubing. Contrary to general belief, higher haemolysis rates occurred with this type of a pump when operated at a pumping rate of 5 liters per minute. 1

Any contact with nonorganic surfaces damages the blood. Metallic surfaces and mechanical compression of parts have had an adverse effect on red cells, platelets and plasma protein. A pump of low breakdown rate should provide (1) a minimum of moving parts, (2) prevent contact of blood with mechanically compressed parts, and (3) convey the blood through flexible ducts and structures with smooth interior surfaces. A mechanical pump should be capabale of delivering about four to six liters of blood in one minute while undertaking the heart action with a smooth, gentle pressure on the fluid. In addition, a blood pump should feature relatively simple means for dismantling and sterilizing the pump parts and be readily adaptable for use with various type oxygenators.

An object of the present invention therefore is to provide an improved pump for pumping fragile type biological fluids wherein the pumping action overcomes many disadvantages of previous pumps which were specified for extracorporeal circulation in man.

Another object of this invention is to provide a pump with flexible valves of novel design which. are more effective in minimizing damage to blood during the pumping action.

A further object of the invention is to provide a pump for extracorporeal blood circulation that can be adjusted to circulate any desired quantity of blood in a given time interval, this being effected by relatively simple adjustments while the pump remains in operation. Similarly,

Patented Nov. 23, 1965 the pump may be adapted for emergency service to operate during electrical power or mechanical failure, and an attendant may even operate the flexible chamber by hand when surgical expediency or the patients condition will so dictate.

A still further object of the invention is to provide a mechanical device that mimics the rhythmical expansion and contraction of the heart, the blood flow remaining uniform and gentle even when the reciprocating action of the diaphragm is adjusted to wide values of frequency and amplitude. The hydraulic action in accordance with the present invention provides a blood flow which is not subjected to mechanical strain as previously experienced by tubular pumps in which the flexible wall was distorted through compression or squeezing. The output of the present hydraulic pump is considerably more efficient since it is not dependent upon peripheral resistance.

Numerous other objects and advantages of the invention will become more readily apparent as the description proceeds.

In the accompanying two sheets of drawings forming a part of this specification an illustrative embodiment of the invention has been shown by way of example.

In the drawings:

FIGURE 1 is a perspective view of a hydraulic blood pump in accordance with the invention, the View being broken away in parts to show the internal structures;

FIGURE 2 is a longitudinal cross section view of the pump chamber during the pressure stroke;

FIGURES 3 and 4 illustrate the valve structures in closed and open views, respectively; and

FIGURE 5 is a fragmentary view partly in section of a bellows diaphragm which is a modification of the hydraulic pressure system shown in FIGURE 1.

Broadly stated, the invention comprises a hydraulic type pump in combination: a container filled with hydraulic liquid, a compressible, hollow chamber formed of an elastomeric material such as rubber or a rubber substitute, a pair of openings in its wall, an inlet and an outlet valve associated with said openings to provide a unidirectional liquid flow through said chamber, and a diaphragm closure in said container for transducing pressure to the hydraulic medium. The application of hydraulic pressure causes the spherical chamber to be uniformly compressed at essentially all points on its surface. The chamber is compressed evenly on its entire surface resulting also in an even distribution of pressure on the internal liquid which is being pumped. The inlet and outlet valves in the pump chamber are characterized as flexible flap closures that serve to seal olf the inlet and outlet passages to the chamber; said valves are yieldably responsive to a relatively slight fluid pressure to control the opening and closing positions of said valves. As a result of the present combination of a compressible sphere and flexible valve closures, the pumping action of the present apparatus is well-suited for circulating a fragile type liquid such as whole blood.

The valved action in the hydraulically compressed chamber is obtained by means of a tubing with a thin, tapered section or projection which is slit laterally at the tapered end to form a more yieldable closure. The closure at the tapered end is preferably a point contact having a minimum of occluding surface. The tapered projection is yieldably distended under any slight pressure from within the chamber permitting blood to pass through the opening, and said projection is yieldably closed by a slight back pressure. The present valve structure is more effective in preventing haemolysis, since the blood is not subjected to occluding surfaces; it also improves the flow rate and provides ease in sterilization of the pump chamber.

An important feature of the present invention is that the blood medium passes through the pulsating chamber with considerable ease, the blood is not experiencing turbulent flow or eddy currents during the pumping action. The flexible flap valves close with a wiping action which repels the liquid away from the closure and reduces local areas of high pressure contact. The spherical chamber is not distorted by hydraulic pressure, and therefore, the blood medium is not subject to the uneven distribution of force as is apt to occur in mechanically compressed flexible tube pumps.

Referring now to the drawings in detail and in particular to FIGURES l and 2, the pump construction involves in its general arrangement a hydraulic system shown in the drawing as a cylindrical transparent container 11 of glass or plastic composition filled with any hydraulic medium 12 and having a removable cover 13. Immersed in the hydraulic medium is a hollow, spherical chamber or bulb 14 of resilient, compressible material, such as rubber, or a synthetic material of a similar character to rubber that has sufficient elasticity to return to its original shape after having been compressed by hydraulic pressure. Flexible tubing 15 is connected to inlet valve 17 on one side of the chamber and similarly flexible tubing 15a is connected to outlet valve 18 on the other side of said chamber. The blood to be pumped is drawn through tubing 15 to fill chamber space 16 and is then forced out through tubing 15a. The flexible tubing is joined to rigid tubular posts 19 which are sealed through the cover lid. An air-tight connection is assured by applying an adhesive cement between said posts and tubing; a clamp (not shown) is then tightened over the junction. A press valve 20 inserted through the cover plate allows air to escape from the container whenever said container is being filled with hydraulic fluid.

Forming a closure to the lower opening of said container is a flexible diaphragm 26 formed of rubber and adapted to move upward into the container to exert pressure on the enclosed hydraulic fluid and in a reciprocating movement to move downward to relieve the pressure on the fluid. A pair of center disks 27 mounted one on each side of said diaphragm stiffen the center area of said diaphragm and also reduce excessive motion in the moving diaphragm. The outer edge of said disks is preferably flared to prevent a crease from forming in the flexible rubber. The disks may be mounted by any suitable metal-to-rubber seal, or they may also be assembled together by a series of threaded bolts and nuts for the convenience of replacing the rubber diaphragm. The diaphragm forms a sealable closure with the bottom edge of the container by means of a right angle collar 28; the diaphragm is inserted between the collar and the surface of casing 29 and fastened thereto by means of threaded bolts.

Still referring to the closures of said container, the bottom edge of said cylinder rests on the right angle collar, While the outer surface of the cylinder is sealed to the vertical side of the collar by a glass-t-o-metal or plasticto-metal seal, as the case may be. Aflixed to the cover lid 13 is a sealing gasket (not shown) to provide an airtight closure. For rapid assemblage, the cover lid and cylinder may be threaded fastened together by a relatively small turn, or the lid may be attached to the cylinder by any suitable clamping means, as is well known in the art.

Within casing 29 is the actuating mechanism for moving said diaphragm: a driving means or motor 31 provides movement through a crank pin 34 slidably disposed within linear slot 33 in one end of the rocker arm 32. A clevis 35 in the other end of said arm is joined to the flattened end portion 36 of push rod 37 secured to the lower center disc 27 by means of pin 40. The rocker arm is pivotally supported on a support arm 39 by a load pin 41 which passes through linear slot 33 to provide an adjustable pivot point to said rocker arm. The support arm 39 extends vertically from a horizontal bar 38 which is adapted for horizontal movement. The variable pivot point changes the vertical distance through which the push rod raises and lowers said diaphragm. The actual distance that the diaphragm will move into the hydraulic fluid during each compression stroke is a function of the length of said rocker arm from the pivot point, maximum pressure stroke being applied on the hydraulic fluid when support arm 39 is moved forward in the direction of the motor. The horizontal bar is slidably mounted within a U-shaped channel 30. A guide pin 42 extending laterally from said bar moves within a rectangular channel 43 to guide the adjustable movement of said support arm along the path of said channel. A flatsurface, calibrated screw 44 extending from said bar provides reference points for accurate positioning of said arm. A knurled-head wheel 45 in threaded engagement with said screw enables the operator to obtain a more accurate and convenient adjustment of the same.

An electric control 47 provides a suitable means for varying the speed of the motor in order to regulate the pumping rate of the pump by the number of compression strokes per minute. The motor is rated at about -80 cycles/minute. The blood pulse rate is thus suitably established and maintained by the rate of compressions (frequency) of the pump chamber. In addition, the blood pressure stroke, based on the amount of blood pumped per stroke of the pump is readily adjusted by wheel 45, as described above.

As the pump structure is depicted in FIGURE 1, a handle 48 is adapted for manual rotation of the motor. The handle is used to adjust the position of the diaphragm when the container is being filled with hydraulic fluid.- In order to benefit fully from a compression stroke, the diaphragm is adjusted to its lowest position, and the container is then filled to capacity, care being taken to exhaust the air from the container. The compression stroke begins when the diaphragm moves upward from its lowest position and continues until it has been raised to its highest position in the container.

Manual operation of the pump becomes critical under emergency conditions, during power failure or mechanical defect, when pump failure means complete stoppage of heart circulation. As a final measure, either manual cranking of handle 48 is resorted to, or the pump chamber may be removed from the hydraulic system and manipulated by hand to promote or resume blood circulation under adverse conditions.

The pump chamber being a readily replaceable item in the present pump structure, a number of said chambers with valves and connecting tubing may be mounted ini tially on lids, as shown in FIG. 1, autoclaved and indi vidually stored in glass jars, containing distilled solution, the lids forming closures for said jars.

Whenever a chamber is to be replaced in the container, it has been found advantageous to reduce the amount of hydraulic fluid in said container to prevent spillage and overflow during the replacement. A reservoir 49 mounted on a vertical track (not shown) is raised and lowered to transfer a certain amount of liquid. A conduit line 51 fitted with a closure valve 52 passes into the reservoir near the collar 28. When hydraulic fluid is to be drained from the container, the reservoir is lowered sufliciently so that the fluid in the container upon seeking its own level passes into the reservoir. After the chamber has been replaced and the lid fastened to the container, the reservoir is then raised and fluid is transferred to the container, care being taken to bleed the air from the container. Valve 52 is then turned shut and the hydraulic system is again ready for operation.

Referring to FIGURES 2, 3 and 4 where a sectional view of the chamber and valves is shown, the spherical bulb 14 has thickened wall sites at the openings, as is commonly the practice with aspirator bulbs. A sleeve 21 in each opening retains the flexible flap valves therein. The inlet valve 17 extends into the chamber space and is attached to the inner wall of sleeve 21. During the pressure stroke, as depicted herein, the blood fluid in space 16 applies an external pressure on the tapered band 22, shown in greater detail in FIGURE 3, lateral slits on each side of the closure provide means for greater ease in distending the tapered portion of the valve when liquid passes through tubing 15. The outlet valve 18 is attached entirely within the sleeve 21. The open outlet valve is shown in perspective in FIGURE 4 wherein the slit 23a distends under pressure from the blood and allows the blood to pass through the opening.

When the pump described herein is placed into operation, lengths of rubber or polyvinyl tubing that have been sterilized and irrigated with distilled water connect post 19 of the outlet side through a flowmeter and oxygenat-or to the arteriovascular system of a patient and by re-v turn tubing to a reservoir and to post 19 of the pump inlet. Fresh blood is introduced into the pump for initial priming. The pulse rate is set by adjusting the speed control 47 and the pressure stroke is set by adjusting-the screw reading 44 to the desired flow rate.

With reference now to FIGURE 5 wherein is shown a modification of the pressure means, 24 designates a bellows type diaphragm which may be operatively disposed as a part of the cylindrical container for applying pressure on hydraulic fluid 12. The bellows which is cylindrical in shape, formed of polyvinyl or other plastic composition, has a series of convolutions 25 that may extend to include the entire hydraulic fluid within its interior. A center disk 27a provides rigid support to the bellows during the compression and return stroke of the pump. The bellows operates in the same manner as the diaphragm closure shown in FIGURE 1. A particular advantage of the present modification is found in the slight flexing action of the bellows which is suflicient for transmitting considerable hydraulic pressure on chamber 14.

The present invention provides a much sought solution to the problem of pumping whole blood without damaging the living cells and also in obtaining a smooth blood flow without foaming action. By applying hydraulic pressure to a spherical chamber fitted with flexible type flap valves, it is possible to pump whole blood at suitable pumping rates without foaming action. Furthermore, a blood pump constructed in accordance with the present invention provides for relatively simple adjustments which are effective for controlling blood pulse and pressure during the operation of the pump. A further advantage is its ability to be combined with simple oxygenators, such as the rotating disks which eliminate the need for defoamers.

It should be understood, of course, that the foregoing disclosure relates to a preferred embodiment of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A hydraulic blood pump comprising:

a sealed cylinder filled with hydraulic fluid and provided with a detachable lid,

a compressible rubber bulb secured within said sealed cylinder and provided with valved inlet and outlet connections,

an inlet valve and an outlet valve in said valved inlet and outlet connections,

each of said valves comprise a tubular section having a thin tapering end, said end having lateral slits therein forming a yieldable closure,

a flexible diaphragm forming a sealed closure with the bottom of said cylinder,

a raised platform for supporting said cylinder,

an opening in said platform substantially the area of said diaphragm,

a rod extending downward from said diaphragm,

a rocker arm pivotally connected with said rod,

said arm being pivotally mounted on an adjustable support to provide a pressure stroke to said diaphragm,

said support being mounted on a movable bar for adjusting the pivot point of said rocker arm and consequently the pressure stroke of said diaphragm, and driving means connected to said arm to produce a rocking motion in the same thereby varying the vertical movement of said rod.

2. A hydraulic blood pump in accordance with claim 1 which includes a hydraulic fluid reservoir, conduit connecting said reservoir to said container and a fluid control means in said conduit connecting said reservoir to said container.

3. A blood pump comprising:

a sealable cylinder for containing hydraulic fluid,

a compressible chamber secured within said sealable cylinder said chamber provided with valved inlet and outlet connections,

an inlet valve and outlet valve in said valved inlet and outlet connections respectively,

each of said valves comprising a tubular section having a thin tapered end, said end having lateral slits therein forming a yieldable closure,

a flexible diaphragm for forming a sealed closure with the bottom of said cylinder,

a raised platform for supporting said cylinder,

an opening in said platform substantially the area of said diaphragm,

a rod extending downwardly from said diaphragm along the axis of said sealable cylinder,

a rocker arm pivotally linked with said rod,

said rocker arm being pivotally mounted on a support member,

means associated with said support member for varying the pivotable point of said rocker arm with respect to said support for varying the vertical movement of said rod, and

drive means connected to said rocker arm to produce a rocking motion in the same thereby varying the vertical movement of said rod.

4. A pump which comprises:

a sealable cylinder having upper and bottom ends for containing a fluid therein,

a detachable cover for said upper end of said cylinder arranged for quick release by hand,

a compressible chamber adapted to be secured within said sealable cylinder,

a valved inlet and outlet in said compressible chamber,

an inlet line and outlet line passing through said detachable cover for connecting respectively with said valved inlet and outlet of said chamber,

a flexible diaphragm forming a sealed closure with the bottom end of said cylinder,

and means for varying the movement of said diaphragm in an axial direction along the cylinder toward and away from said upper end to compress said compressible chamber when secured within a fluid within said cylinder to produce a pumping action therein,

whereby said detachable cover along with said compressible chamber may be removed from said cylinder and pumping action on said chamber produced by hand upon failure of said means for varying the movement of said diaphragm.

5. A pump which comprises:

a sealable cylinder having upper and bottom ends for containing a flluid therein,

a detachable cover for said upper end of said cylinder arranged for quick release and removal,

an inlet line and outlet line passing through said detachable cover and secured thereto,

a compressible chamber secured from said detachable cover for placement into said cylinder,

an inlet and an outlet in said compressible chamber,

a one Way valve in said inlet for admitting a fluid into said compressible chamber,

a one way outlet valve in said outlet for permitting fluid to flow from said compressible chamber,

means for connecting said inlet line to said inlet in said compressible chamber,

means for connecting said outlet line to said outlet of said compressible chamber,

means for securing said detachable cover onto said cylinder with said compressible chamber confined within said cylinder,

a flexible diaphragm forming a sealed closure with the bottom end of said cylinder,

and means for varying the movement of said diaphragm along the axis of, said cylinder to compress said compressible chamber when confined within a fluid within said cylinder to produce pumping ac- 15 tion therein, whereby said detachable cover and said compressible chamber may be removed from said cylinder and pumping action on said compressible chamber may be produced by hand upon failure of said means for varying the movement of said compressible chamber.

References Cited by the Examiner UNITED STATES PATENTS 862,867 8/1907 Eggleston 230l70 2,812,716 11/1957 Gray l0344 3,099,260 7/1963 Birtwell 103-44 FOREIGN PATENTS 688,346 8/1930 France. 496,227 7/ 1954 Italy.

ROBERT M. WALKER, Primary Examiner. 

1. A HYDRAULIC BLOOD PUMP COMPRISING: A SEALED CYLINDER FILLED WITH HYDRAULIC FLUID AND PROVIDED WITH A DETACHABLE LID, A COMPRESSIBLE RUBBER BULB SECURED WITHIN SAID SEALED CYLINDER AND PROVIDED WITH VALVED INLET AND OUTLET CONNECTIONS, AN INLET VALVE AND AN OUTLET VALVE IN SAID VALVED INLET AND OUTLET CONNECTIONS, EACH OF SAID VALVES COMPRISE A TUBULAR SECTION HAVING A THIN TAPERING END, SAID END HAVING LATERAL SLITS THEREIN FORMING A YIELDABLE CLOSURE, A FLEXIBLE DIAPHRAGM FORMING A SEALED CLOSURE WITH THE BOTTOM OF SAID CYLINDER, A RAISED PLATFORM FOR SUPPORTING SAID CYLINDER, AN OPENING IN SAID PLATFORM SUBSTANTIALLY THE AREA OF SAID DIAPHRAGM, A ROD EXTENDING DOWNWARD FROM SAID DIAPHRAGM, A ROCKER ARM PIVOTALLY CONNECTED WITH SAID ROD, SAID ARM BEING PIVOTALLY MOUNTED ON AN ADJUSTABLE SUPPORT TO PROVIDE A PRESSURE STROKE TO SAID DIAPHRAGM, SAID SUPPORT BEING MOUNTED ON A MOVABLE BAR FOR ADJUSTING THE PIVOT POINT OF SAID ROCKER ARM AND CONSEQUENTLY THE PRESSURE STROKE OF SAID DIAPHRAGM, AND DRIVING MEANS CONNECTED TO SAID ARM TO PRODUCE A ROCKING MOTION IN THE SAME THEREBY VARYING THE VERTICAL MOVEMENT OF SAID ROD. 